This disclosure relates to an image forming apparatus having a charging function.
In recent years, image forming apparatuses, such as printers, copiers, and multifunctional peripherals, are widely available and also installed at establishments that are accessible to an unspecified large number of people, such as convenience stores and public facilities in addition to offices. These image forming apparatuses available for use by people make charges users and collect fees for use.
For example, a charge for image formation including copying is made every time an image is formed on a sheet of paper at a unit price predetermined in accordance with paper sizes and color modes set by selecting monochrome, full color or the like. Even an image forming apparatus installed in an office, that is, in an environment accessible to only specified users, is programmed to measure the usage for each individual or each department, for example. The usage is utilized for cost allocation or the like, and therefore can be regarded as a kind of charge.
When an error, such as a paper jam, occurs during image formation, image forming apparatuses suspend the image forming operation, and then require the user to remove the jammed paper. In this case, charging the user for an incomplete printout caused by the error is a problem. To solve the problem, some image forming apparatuses are programmed not to charge for the possible incomplete printout.
However, adopting a mechanism for uniformly stopping charging for such possible incomplete printouts can possibly provide users with opportunities to acquire printouts at no charge. For example, if a malicious user intentionally induces an error by opening a cover of an image forming unit or other devious ways, the user can obtain sheets on which images have been completely formed in the image forming apparatus as of the point in time, at no charge.
As a measure to prevent this, some known image forming apparatuses determine whether or not to execute charge processing based on presence or absence of a sheet that has already passed a fuser and has become a subject to be charged at the occurrence of an error.